I get very fast download speeds but almost nonexistant upload speeds?

[55]

According to speedtest.net I should have over 11 mbps for both. Whenever I use a torrenting program I'll get download speeds of about 800kb/s-1mb/s but upload speeds anywhere between 0-2 kb/s. When a torrent is finished it will not seed any more, regardless of the number of peers on the torrent. Having an active upload or download going, even if it's not doing anything, will often completely cripple my ability to use the internet; no pages will load unless I stop the download.
For a while I didn't have this problem, in that it would seed, upload, and not kill my internet, but even in the best of days, I've gotten about 30 kb/s upload to 1 mb/s download.
I think I've had this problem as long as I've had this computer?? I'm pretty sure it's this machine and not the fault of my isp.
How do I fix this?

[Joseph Zimmerman]

Make sure you use port forwarding and that port is open for torrent traffic. Use uTP, turn off DHT, PeX, LPD unless the trackers have blocked your ip. Uploading speeds would max out if there are less seeders and more leechers when you have a port open.